1. Field of the Invention
The invention relates to a pipe clamp, in particular, a pipe coupling, comprising a tightenable clamp body with at least one spike strip arranged radially inwardly within the clamp body and slanted toward the axial center of the clamp body. The spike strip delimits an acute angle between it and the radially inner side of the clamp body and has teeth at one longitudinal edge which teeth project radially inwardly and are slanted axially relative to the clamp body. It is supported in the area of the other longitudinal edge in the radial direction and in the axial direction on the clamp body.
2. Description of the Related Art
Such a clamp serves either for coaxially connecting smooth end sections of pipes and/or as a holding clamp in connection with an additional support or fastening part for attachment on building parts.
When the pipe clamp is used as a pipe coupling, it has at its two axial ends a spike strip arrangement, respectively, wherein each spike strip arrangement is comprised of two or more spike strips. The teeth of the spike strips at the axial ends of the clamp body are facing one another. This has the effect upon tightening the clamp body that the pipe ends cannot easily be pulled apart again.
However, mounting of such a pipe clamp is relatively complex. Tightening of the clamp body must be realized with relatively high precision. Generally, this requires the use of a torque wrench.
It is an object of the present invention to simplify mounting of such a pipe clamp.
In accordance with the present invention, this is achieved in that the acute angle is free of means counteracting a bending of the spike strip toward the radially inner side of the clamp body.
In other words, the spike strip rests only with one longitudinal edge on the clamp body and projects otherwise freely to the center axis of the clamp body. On the backside of the spike strip delimiting the acute angle between the spike strip and the clamp body there is no element which could act as an abutment for the spike strip. When the clamp body is tightened, the teeth of the spike strip can be pushed radially outwardly. Since the spike strip is elastically yielding in a certain way, this results in a certain spring action. The teeth and the pipe ends accordingly are engaged with increasing grip the tighter the clamp body is tightened. Moreover, the slanted teeth ensure that the two pipe ends with increasing tightening of the clamp body and the resulting diameter reduction of the clamp body are moved toward one another and can approach one another with a certain predetermined force. At the same time, an adaptation to different diameters of the two pipe ends is possible. The spike strip at the pipe end with the greater diameter is adjusted more with regard to its contact angle. Since the spike strip is without abutment on its backside, it can be unimpededly pushed or bent radially outwardly. This increases at most the contact force of the teeth on the pipe but does not result in overloading of support means of any kind.
Preferably, the spike strip rests on the clamp body in the area of the other longitudinal edge, wherein the clamp body and the spike strip have matching contact shapes which receive pressure forces in the axial and radial directions. In this way, across the greater part of the circumference of the clamp body there is no permanent attachment required between the clamp body and the spike strip. It is sufficient when on the clamp body and/or on the spike strip shaped portions are provided which support one another such that the spike strip can be moved in an axial direction relative to the clamp body. A movement in the radial direction (relative to an annular clamp body, respectively), is not possible anyway because such a radial movement is prevented by the clamp body.
It is particularly preferred in this context that the clamp body has a radially inwardly bent edge portion which forms an inner angle in which the other longitudinal edge of the spike strip is arranged. Accordingly, the clamp body is bent at its axial ends so that the clamp body, in cross-section, has a U-shaped profile or a C-shape profile open radially inwardly. When the spike strip is now positioned into the corner of the profile, wherein the spike strip together with the clamp body delimits an angle in the range of 15xc2x0 to 75xc2x0, the edge portion provides a sufficient support relative to a movement of the spike strip relative to the clamp body in the axially outward direction. The clamp body itself provides a sufficient abutment relative to a movement radially outwardly. When the tension in the clamp body increases because the clamp body is positioned somewhat tighter about the pipe, the spike strip cannot yield or move away but can only elastically yield in the direction toward the clamp body wherein possibly the angle between the spike strip and the clamp body changes; otherwise, no change in the geometry can be observed.
Preferably, the spike strip is connected with its ends to the clamp body. This embodiment is particularly advantageous when in the circumferential direction of the pipe clamp two or more spike strips are provided. When the spike strip is a ring, optionally also in the form of a ring which is interrupted once, it is sufficient in many cases to simply place the ring into the clamp body. When, on the other hand, several ring sections are provided, the attachment of the ends of the spike strip prevents that the spike strip can be lost. Moreover, the fixation of the spike strip on the clamp body achieves that the clamping forces can be generated with sufficient precision where they are supposed to act.
Preferably, the spike strip is positive-lockingly connected with the clamp body. A positive-locking connection can be produced in a simple way. It requires no complex additional measures such as welding, soldering or gluing. It is only required to shape certain areas of the clamp body and/or of the spike strip so that the corresponding connecting geometry can be produced. The positive-locking connection is limited to the ends of the spike strip.
In this connection it is particularly preferred that the clamp body and the spike strip are connected to one another by hoops which are formed as a unitary part of the clamp body and positive-lockingly connected with the spike strip, or formed as a unitary part of the spike strip and positive-lockingly connected with the clamp body, or positive-lockingly connected with the spike strip and the clamp body. Such a configuration can be produced relatively simply. It is sufficient to stamp certain parts and to bend them. This can be carried out during the stamping and bending processes which are required anyway for producing the pipe clamp.
Preferably, on each one of the spike strips a hoop is connected on at least two sides of the hoop with the clamp body and forms a pocket into which the spike strip can be inserted. Such a configuration of the hoop increases the stability and strength of the connection of the hoop with the correlated part of the clamp body or the spike strip. For attachment of the spike strip on the clamp body, a movement of the spike strip relative to the clamp body is required. However, this can be realized in most situations.
In this connection, it is advantageous when the hoop is fastened with one end while it can be bent open at the end. In this way, the bending process upon attachment of the spike strip on the clamp body is limited to the hoop so that neither the clamp body nor the spike strip must be deformed.
Preferably, one end of the hoop is fastened on the edge portion. In this way, the hoop can begin already at a certain radial spacing from the clamp body, i.e., in certain situations one or the other bending process can be omitted. In particular when the hoop is fastened with both ends on the clamp body, no extension of the hoop itself is required.
Preferably, the spike strip has at least at one end a fastening portion which is rotated relative to the remainder of the spike strip. As already mentioned, the spike strip and the clamp body together delimit an acute angle. This angle would also be provided at the fastening portion so that a corresponding great radial extension of the hoop would be required. When instead the fastening portion is rotated somewhat relative to the remainder of the spike strip, the radial length of the hoop can be reduced.
In this connection, it is particularly preferred that the fastening portion is arranged at least approximately parallel to the clamp body. The hoop can then have its minimal radial length. At the same time, when the fastening portion is forced approximately in a planar way against the clamp body, an improved holding of the spike strip on the clamp body is provided.
Preferably, the edge portion in the circumferential direction has at least one interruption. In this way, a hinge can be formed on the clamp body. This facilitates on the one hand the manufacture of the pipe clamp because with a folded-open clamp body a better access to the interior of the clamp body is possible. This is advantageous particularly when positioning the spike strips. On the other hand, mounting or demounting of the pipe clamp by a worker is facilitated because the worker is able to bend the clamp body open, for example, in order to place the clamp about the pipe or pipe ends or to remove it therefrom.
Preferably, the interruption is formed in that the edge portion is bent axially outwardly about a predetermined circumferential length. In this way, it is prevented during tightening that the force lines which form within the clamp body are interrupted. This improves the loading strength of the pipe clamp.
It is also advantageous when the interruption in the circumferential direction is arranged outside of a spike strip. In this way, the function of the hinge is not impaired by a spike strip. Mounting of the spike strip in the clamp body is simplified.
Also, it can be provided that the circumferential length of the clamp body is selected such that its circumferential ends rests against one another when the clamp is tightened to such an extent that the diameter of the circle described by the free tooth ends is smaller than the smallest nominal outer diameter, taking into consideration the pipe diameter tolerance range of the pipe or pipes to be received in the clamp.
In this way, overloading of the parts is prevented so that the clamp body can thus be tightened up to the point of contact of its ends (clamping jaws). Mounting can therefore be monitored visually without requiring measuring instruments of any kind. This means also that a torque wrench is not required. Still, the spike strip remains flexibly prestressed.
The invention will be explained in the following with the aid of a preferred embodiment in connection with the drawing.